The cutting of predetermined shapes from a sheet material may be achieved by using a laser or fluid jet or similar. When using a fluid jet to cut such material is it very difficult to control the depth of cut accurately. Indeed normally the material is cut all the way through its entire thickness with the jet passing through the material from one side another. The sheet material is normally secured by a fixture which supports the sheet material to allow for the jet to pass from one side to the other without the jet being unnecessarily disbursed or impinging on other parts of the fixture. By way of example, a fixture may hold a sheet material above a water filled tank and from the other side of which the jet impinges onto the sheet to cut through the sheet thereafter being directed into the water filter tank to disburse any remaining jet energy.
When it comes to methods to hold the sheet material, limitations arise especially if the jet used to cut the material may, once passed through the material still has sufficient energy to cause damage to the portions of the fixture on the other side of the sheet material. Whilst the sheet material may be held at its perimeter region allowing for a clear passage of cutting fluid to pass through the sheet material and into the tank beneath, the product cut from the sheet material will subsequently fall into the tank of water from which it will need to be removed. The product cut from the sheet material floating around in the tank may become damaged from subsequent jet action being directed into the tank of water. For cutting of small squares or rectangles for example the method of fixing the sheet is of real concern as the jet needs to be able to pass freely through the sheet and then passed the fixture, into the water tank without damaging the fixture. The fixture must simultaneously be designed to support the parts once separated by the cutting action. Where the fixture is able to maintain support to the sheet by extending below and inwardly from the perimeter of the sheet, the cutting of a product from the sheet material is not a problem. However as soon as a product to be cut is to be generated entirely inwardly from the perimeter of the sheet, support by the fixture to that product to be removed from the sheet can no longer occur where the sheet and the fixture remain in a fixed relationship to each other during the cutting process.
Accordingly without providing a hole in the fixture about the product to be cut from the sheet, but to remain supported by the fixture the cutting process can not be performed without the jet also impinging on part of the fixture itself. To avoid the jet impinging on the fixture itself in such a relationship, a hole in the fixture of a greater size to the product to be cut from the sheet must be provided which, once the product is entirely cut from the sheet will result in the product from falling through and away from the fixture.
For certain cutting procedures it is also imperative that a high degree of accuracy of the items cut from a sheet is achieved to within very close tolerances. This is particularly so in relation to the cutting items from a sheet to be used in circuit board or other electronic type applications. Therefore in mounting a sheet for cutting it is desirable for the sheet to remain in a relationship to the cutting device wherein the relationship remains constant such that during a computer controlled cutting of the sheet, no margin of error can be introduced between the relative positioning of the cutting device and sheet as a result of for example the movement of the sheet between different cutting stations.
Accordingly it is an object of the present invention to provide a method and related apparatus for cutting a product from a sheet material which overcomes the abovementioned difficulties or which will at least provide the public with a useful choice.